In general, the technology of a fixed-mobile convergence (FMC) service, which uses a wireless local area network (e.g., WiFi network) indoors and a wireless wide area communication network (also called ‘mobile communication network’) such as 3G/LTE mobile network outdoors, provides terminals with a plurality of networks to access selectively for communication. In other words, the FMC service allows a mobile terminal to be used as a fixed telephone (an extension phone or an office telephone) regardless of whether it is indoors or outdoors.
Therefore, an FMC terminal has at least two wireless interfaces, which may be individually for a mobile communication network and a WiFi network. Using such FMC terminals, users can save service charge by using the FMC service through a WiFi network and carriers can reduce load on their mobile networks.
However, since a WiFi network is used by a large number of users in the same frequency band, there is a problem that the quality of real-time voice calls is not guaranteed due to serious interference. Whereas, an improved mobile communication network such as LTE network is able to provide an FMC service of stable quality for mobile terminals regardless of whether they are indoors or outdoors.
Recently, several carriers released a data rate plan that charges for data usage instead of offering unlimited numbers of voice calls, so that the cost of data usage tends to exceed the cost of voice calls. In this data-oriented communication environment, the cost (for example, the cost due to data consumed in a voice call) burden on subscribers of the FMC service increases. As a result, companies are reluctant to make decision on FMC adoption even though FMC ensures work mobility and increase of productivity.